38 British Vegetable Galls 



on roots. Two are illustrated in this volume, the descriptions 

 of which will be found on plates 36 and 37. 



VIII. The Hymenoptera, or Wasps (Small). 



The insects belonging to the order of Hymenoptera that 

 produce gall are known as Gall-wasps. 



The imago has four wings. The pair on each side of the 

 thorax are held together, while employed in flight, by means 

 of hooklets, or hamuli. 



This order includes bees, wasps (social and solitary), 

 ichneumons, and ants, but none of these appears to produce 

 galls. It is among the family of Cynipidce that the gall-pro- 

 ducing hymenoptera are found. 



The bodies of these insects are of very beautiful and bright 

 metallic colours. Red, green, orange, and blue colours pre- 

 dominate. The wings also are exceptionally iridescent. 



Gall-wasps are very agile and graceful in their movements. The 

 ? ? possess an instrument of very fine and delicate construction 

 known as a seta, or tercbra, which is used for the purpose of 

 oviposition. The terebra is very long, and can be made to pene- 

 trate deeply into the vegetable tissues, or between the scales of 

 a leaf-bud. Each ovum when deposited in a mass of tissue has 

 an elongated appendage known as the eggstalk, the end of which 

 is very near the surface of the plant. From its arrangements 

 and its contents, it has been considered an organ of respiration 

 to convey oxygen to the embryo deep down in the tissues. 



The phenomena of parthenogenesis and alternation of 

 generations are the most wonderful features connected with the 

 Cynipidce. These subjects can be more suitably treated in a 

 contemplated volume on the oak-galls, than here. 



The larva; are apodus, white, and fleshy ; they move very 

 little. The length of time required for development is very 

 variable. The pupa; are white, and all the limbs and the wings 

 can be clearly seen through the puparium. The imagines are 

 peculiar, not only in the manner of oviposition, but in taking 

 no food, and in not frequenting flowers ; they also feign death. 

 All the galls they produce are completely closed, and are of 

 two kinds, soft and succulent, or hard and woody. 



Some species of the CynipidcE disregard the cold of winter 

 and lay their eggs during very unfavourable weather. 



